1. Field of the Invention
This invention relates to lignin/biologically active agent composites. More particularly, this invention relates to the inclusion of a biologically active agent in molecular to droplet or particle size throughout an alkali lignin matrix and the slow release of the biologically active agent from the matrix.
2. Prior Art
Methods of obtaining controlled release of biologically active organic liquids such as drugs and pesticides are numerous in the prior art. For example, one method for obtaining control release of droplet size materials is through microencapsulation, such as that set forth in U.S. Pat. No. 3,516,941 to G. W. Matson. In the Matson patent microcapsules are provided whereby a liquid organic fill is enclosed by a strong, impermeable polymer shell. The microcapsules are produced by dispersing and maintaining the fill material as finally divided particles in an aqueous water-soluble urea-formaldehyde precondensate while polymerizing the precondensate by acid catalyst. In this case, the fill material is released by rupturing the encapsulating material.
Other prior art control release mechanisms have been utilized to control biologically active organic liquids. As presently known, pesticides often have short useful lives because they are degraded by bacterial inactive metabolites, or washed by rain into the subsoil where they are inaccessible to the pest they intend to control, or rendered inactive by volatile loss, or by ultraviolet degradation of sunlight. It is therefore desirable to provide a system whereby proper amounts of a biologically active organic liquid, such as a pesticide, may be continually released over a relatively long period of time. An up-to-date discussion of controlled release of pesticides and the desirability of using controlled release systems was presented by Allan et al. in an article entitled "Pesticides, Pollution and Polymers" in the March 1973 issue of Chem. Tech.
U.S. Pat. No. 3,393,990 to R. J. Geary is directed to a stabilized pesticide composition wherein the pesticide is ground to a fine state of subdivision to exhibit its greatest effectiveness due to maximum availability by virtue of large surface area. The pesticide is held in place with a stabilized interpolymer substrate while it is slowly released.
U.S. Pat. No. 3,172,752 to H. L. Pierce is directed to an article of manufacture for control release of an active agricultural substance. The article is an enlarged particle formed from ground, expanded perlite which is properly sized and heated to drive off water. The expanded perlite particles are coated and impregnated with hardened, slowly soluble holding material of a viscous character before hardening. At least one active agricultural substance is uniformly dispersed therethrough and held to the particle substantially and completely covering the surfaces and completely filling the pores which communicate with the surfaces to intimately and tightly bond the agricultural substance to the perlite particles.
A third method for controlling the release of pesticides is provided in Canadian Pat. No. 863,310 to G. G. Allan. There is disclosed in the Allan patent the chemical co-valent bonding of a pesticide to a lignin polymeric substrate. The pesticide is released by destruction of covalent chemical bonds.
It is therefore the general object of this invention to provide a composite having a biologically active agent interspersed throughout an alkali lignin matrix.
Another object of this invention is to provide processes for interspersing a biologically active agent throughout an alkali lignin matrix via physical contact forming a composite.
It is a specific object of this invention to provide a controlled release pesticide system comprising as a composite, a pesticide interspersed throughout an alkali lignin matrix whereby the release rate of the pesticide is accomplished through diffusion of the active ingredient through the alkali lignin matrix or through degradation or dissolution of the alkali lignin matrix or a combination of both.
It is still another object of this invention to provide lignin composites containing pesticides which are stabilized against the degradation effects of ultraviolet light in the form of sunlight.
It is an even further object of this invention to provide pesticidal containing composites which have control release that are substantially uneffected by rain.
It is yet another object of this invention to provide lignin matrixes containing pesticides which resist and inhibit the action of micro-organisms.
Still another object of this invention is to provide controlled release pesticidal systems which maintain maximum and effective activity over prolonged periods of time under normal plant environmental conditions.
Other objects, features and advantages of this invention will become evident on reading the foregoing detailed description.